Hollow structures are known in the prior art, for example, in the field of face masks for delivering breathable air to a patient. In such face masks, hollow cushions are used for providing contact zones for contacting the face of the user in order to avoid dents and to improve wearing comfort of the user. Furthermore, such structures are used as a sealing structure for sealing the mask interior from the exterior in the contact region where the mask rests on a user's face.
A disadvantage of hollow structures known in the art is that they are complicated to manufacture and a number of manual manufacturing steps is often necessary. Moreover, such hollow structures are either not closed, i.e., open, or are closed in an ineffective and/or complicated manner.
In particular, it is known to fill a mask cushion with silicone or gel wherein the hollow structure is closed by use of a silicone adhesive.
The solutions known in the prior art are in particular, not easy to handle, not durable, complicated and expensive to manufacture, not suitable for automating, not bio-compatible as well as optically and hygienically objectionable.